Properly implement identical() test in analyzer constant evaluation.

tests/language/identical_const_test.dart

+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'package:expect/expect.dart';
+
+f() {}
+const g = 1;
+
+const identical_ff = identical(f, f);
+const identical_fg = identical(f, g);
+const identical_gf = identical(g, f);
+const identical_gg = identical(g, g);
+
+// Verify proper compile time computation of identical()
+const a = const {
+  identical_ff: 0, /// 01: static type warning
+  identical_gg: 0, /// 02: static type warning
+  true: 0 };
+
+const b = const {
+  identical_fg: 0, /// 03: static type warning
+  identical_gf: 0, /// 04: static type warning
+  false: 0 };
+
+use(x) => x;
+
+main() {
+  use(a);
+  use(b);
+
+  // Verify proper run time computation of identical()
+  Expect.isTrue(identical_ff); /// 05: ok
+  Expect.isTrue(identical_gg); /// 06: ok
+  Expect.isFalse(identical_fg); /// 07: ok
+  Expect.isFalse(identical_gf); /// 08: ok
+}